An analogue of a toxic gliadin peptide as a possible basis for induction of tolerance in coeliac disease

OBJECTIVE: Tissue transglutaminase is the antigen for antiendomysial antibodies, whose power in screening for celiac disease is well known. Our aim was to assess the efficacy of an ELISA assay for tissue transglutaminase antiodies. METHODS: Tissue transglutaminase antibodies were analyzed in serum from 39 untreated celiac disease patients and 61 controls. Tissue transglutaminase was used as antigen, and test sera analyzed by ELISA. Results higher than 0.6 optical density were considered positive, lower than 0.4 negative, and between 0.4 and 0.6 borderline. RESULTS: Optical density of the serum from the patients with untreated celiac disease (median: 1.41; range: 0.33-1.47) were significantly higher than the controls (median: 0.32; range: 0.17-0.68; p < 0.0001; 95% confidence interval 0.87-1.08). Thirty-three patients with untreated celiac disease were positive, 4 borderline, and 2 negative. Fifty-five controls were negative, 4 borderline, and 2 positive. If we consider borderline results to be positive, sensitivity is 94.8% and specificity 90.1%. None of the controls gave results higher than 0.7 optical density. Apart from the 2 negative patients with untreated celiac disease, the two groups overlapped only between 0.4 and 0.7 optical density. CONCLUSIONS: Because of the hith sensitivity (approximately 95%) and technical simplicity, tissue transglutaminase antibodies may prove useful for the screening of celiac disease in population at low or medium risk of celiac disease. To avoid duodenal biopsies in patients without celiac disease, the specificity of the screening procedure may be increased by confirming with antiendomysial antibodies by immunofluorescence on human umbilical cord in individuals with results between 0.4 and 0.7 optical densitity

Binding of gluten-derived peptides to the HLA-DQ2 (α1*0501, β1*0201) molecule, assessed in a cellular assay

The nature of the immunopathogenic relationship underlying the very strong association of coeliac disease (CD) to the HLA-DQ (A1*0501, B1*0201) genotype is not known, but probably relates to binding of gluten-derived epitopes to the HLA-DQ (α1*0501, β1*0201) heterodimer (DQ2). These epitopes have not yet been defined. In this study we have tested the binding of various gluten-derived peptides to DQ2 in a cellular assay using Epstein–Barr virus (EBV)-transformed B lymphocytes and murine fibroblast transfectants. One of these peptides (peptide A), which has previously been shown to exacerbate the CD lesion in vitro and in vivo, was found to bind to DQ2, albeit only moderately, lending further credence to its possible role in the pathogenesis of CD. The nature of peptide A's binding to DQ2 was explored with truncated and conservative point substituted analogues and compared with the published DQ2 binding motif, the results of which explain the observed level of binding

Anti-α-gliadin antibodies (AGA) in the serum of coeliac children and controls recognize an identical collection of linear epitopes of α-gliadin

Anti-gliadin antibodies can be found in the serum of patients with overt and subclinical coeliac disease, but also in that of some controls. The aim of the present study was to identify the linear epitopes of the α-gliadin molecule to which the humoral response is directed. Therefore, the IgG and IgA antibody reactivity against an overlapping set of synthetic peptides covering the entire sequence of α-gliadin was measured in the sera from patients with coeliac disease, from controls with elevated titres of anti-gliadin antibodies and from healthy children using an ELISA technique. The antibodies mainly recognize peptides derived from the N-terminal region of α-gliadin, containing the motif QPFXXQXPY. Reactivity was also detected against two other synthetic peptides, which do not contain this motif and represent a sequence encoded further to the C-terminal region of α-gliadin. Anti-gliadin antibodies in sera from patients with coeliac disease and from controls recognize the same linear epitopes. Thus, serological investigation of the specificity of these antibodies using a peptide ELISA does not allow discrimination between patients and controls